The 1,280-pupil Penglais School, a state comprehensive, enforced the strict uniform changes to coincide with the arrival of its new headteacher Mair Hughes.

But around 450 schoolchildren are said to have been sent to detention yesterday(TUE) on the first day of term, with many parents saying their children's footwear was apparently to blame.

One mother at the school in Aberystwyth, West Wales, said her daughter was punished for not wearing leather shoes, despite explaining to teachers she was a vegetarian.

And another said she'd spent £50 on her son's black, leather polished shoes only to be punished for being the wrong shape.

Another parent, Kelly Hughes, said: "My daughter was given detention on the first day back. I am so cross as I have bought shoes to match their description - all black, leather, polishable, flat smart shoes - and apparently they are not in the policy.

"She's been told that she will have one hour and 20 minutes of detention today and after school tomorrow if she doesn't get another pair of shoes."

"They are black and flat, they pulled her up on the fact that they are not leather. When she explained that she's a vegetarian and doesn't want to wear leather she was told that was not a good enough reason.

"She's been told she will have detention until she sorts her shoes out. I'm fed up with it. Let the kids have a bit of individuality and expression for goodness sake.

"Putting them into a strict school uniform is ridiculous, and then punishing them with endless detentions is totally unfair."

A letter sent last Tuesday by assistant headteacher, Andrew Barlow, said: "Footwear for school must be formal and not include canvas shoes, vans, pumps, trainers or any leisure shoes."

The rules were posted the same day on the school's website, demanding pupils wear a bespoke Rowlinson "Performa 50" jumper, tailored trousers, formal, knee length skirt for girls, and a requirement for shirt top buttons to be done up.

A spokesman for Ceredigion Council said: "We understand that many Ysgol Penglais pupils were given detention during break for not complying with the school uniform policy.

"Following some confusion about certain aspects of the uniform, we understand that the school will now be writing to parents to further clarify their expectations."